About to start shattered star campaign and we don't have a rogue in the party. Should I get 1 level of rogue and then ranger or go Urban Ranger, must admit I don't like losing the chosen terrain benefit. I am going archer ranger fyi with 20 point buy. Any thoughts or suggestions.?

Assuming the point is getting the trapfinding ability of a rogue, i would suggest checking all archetypes that also have it:
http://www.google.com/cse?cx=006680642033474972217%3A6zo0hx_wle8&q=trap finding
(click on classes in the header bar, to limit search to classes)

For a ranger there is also the trapper archetype, has trapfinding and gives up spell casting for traps, but has normal favored terrain of ranger.http://www.d20pfsrd.com/classes/core-classes/ranger/archetypes/paizo ---ranger-archetypes/trapper

I do not think its strong, but if you do not like the ranger spell casting, then its ok. At lev 10 traps can be used in combat by preparing arrows ahead of combat.

Also, then other ranger archetypes are possible. Beastmaster with boon companion feats is nice. Freebooter, although quite off topic, is nice for having and always avaiable move activated bonus instead of a only sometimes useful fav enemy.

and furthermore rogue lev 2 to 4 gives also each +1 bab, so maybe even more levels in rogue could be useful, without reducing combat capabilities much.

E.g. if traps are realy a concern and the gm follows the rules the rogue talent for autopreception near traps is a must have at lev 2 rogue. (most people seem to houserule, that perception vs trap is checked anyway, per rules only while searching, which nobody does, cause it would take so long, that 1-hour and 10 mins buff would have to be recast.)

i just realized, that the alchemist crypt breaker archetype can also gain autoperception rolls vs traps via discovery.

That might be better choice than rogue, if autoperception rolls for traps are needed, as crypt braker alchimist has more useful stuff than rogue, unless the skill ranks are needed.

E.g. crypt braker alchimist can spend a feat to gain mtagen discovery, so he can mutagen for 20-40 mins per day (depending on how far the dip goes) or gain an extra arm to use a medium shield for +2 (or more) AC.

Rogue gets sneak anytime the target is Denied the Dex bonus (or when flanking ... you cannot flank at range however). Being flatfooted is merely one way to be denied your dex bonus. See the Combat section for more ways end up denied your dexterity.